Extra Characters
To unlock the final 3 hidden characters, select the 'Challenge' option on the main menu:

Matsuritchi - Get gold medals on all 'Mini-Games' and 'Gotchi Games'.
Purimatchi - Get gold medals on all 'Mini-Games' and 'Gotchi Games'.
Shitiketchi - Get gold medals on all 'Mini-Games' and 'Gotchi Games'.